Portable bridges



Feb. 24, 1970 w. A. KAUFMAN 3,496,586

PORTABLE BRIDGES Filed May 6, 1968 4 Sheets-Sheet 1 Feb. 24, 1970 w. A. KAUFMAN PORTABLE BRIDGES 4 Sheets-Sheet 2 Filed May 6, 1968 FlG.5

Feb. 24, 1970 W.A. KAUFMAN ronmsnn munems 4 Sheets-Sheet 3 Filed May 6, 1968 Feb. 24, 1970 WA. KAUFMAN PORTABLE BRIDGES 4 Sheets-Sheet 4 Filed May 6. 1968 FIG. 8

FIG. 9

United States Patent 3,496,586 PORTABLE BRIDGES William A. Kaufman, Alvin, Tex., assignor to The Griifolyn Co., Inc., a corporation of Delaware Filed May 6, 1968, Ser. No. 726,784 Int. Cl. E01d /14; B63d /34 US. Cl. 14-27 6 Claims ABSTRACT OF THE DISCLOSURE A portable, foldable bridge comprises cellular filler between two fiber reinforced foldable plastic film laminates, provided with transversal stiffeners and a protective siding. This siding may be a buoyant rollable apron which when rolled up forms a highly buoyant protective longitudinal member.

This invention relates to portable bridges, and more particularly to a portable bridge made substantially of reinforced plastic film, and adapted to float on, and being supported by, the water which it bridges.

Heretofore various types of pontoon bridges have been employed, in which more or less rigid members have connected a number of substantially rigid buoyant pontoons. Floating bridges have been made of connected wooden logs or the equivalent.

Prior flotation bridges constructed of plastic films and polyethylene foam supported by ropes are unable to withstand the side pressure of the water in moving streams and rivers. This results in the sides collapsing inward and water spilling in.

The present invention has for its object a floating bridge of exceptional lightness and portability.

Another object is a bridge which owes most of its buoyancy to a boatlike structure in which the sides of the bridge, like the sides of a boat, prevent the water from washing over the bridge, thus greatly enhancing its buoyancy.

Another object is a bridge having buoyant, flexible, bendable cylindrical sides.

Further objects will become apparent as the following detailed description proceeds.

. I have discovered that a flotation bridge free from these disadvantages of prior art results, if it is made of a flexible, rollable composite sheet having closed-cell foam positioned between two reinforced plastic film sheets, so that an extra margin of said sheets exists to both sides, and this is rolled up to form highly buoyant unsinkable cylinders on both sides of the bridge, to enhance buoyancy and to prevent water from flooding the bridge from the side.

Reference is made to the drawings, of which:

FIG. 1 is a perspective view of the packaged bridge ready for use or transporting.

FIG. 2 is cross-sectional view.

FIG. 3 is a side view of the portable flotation bridge.

FIG. 4 is a cross-sectional view of the portable flotation bridge.

FIG. 5 is a top view of the portable flotation bridge.

FIG. 6 is a cross-section view of the reinforced film polyethylene foam floatable laminate material.

FIG. 7 is a perspective view, showing the bridge in use.

FIGS. 8 and 9 are sectional detail views.

In order to use the present invention, the packed, rolled up bridge shown in FIGS. 1 and 2 is unrolled, the side pieces 8 (FIG. 4) folded outward and then rolled around the guide ropes 1 (FIGS. 2 and 3) and the longitudinally protruding ends of these guide ropes are tied to fixed objects on both shores (FIG. 7) thus attaching the bridge and raising the sides above the water level 9 (FIG. 4).

3,496,586 Patented Feb. 24, 1970 The rolled up side 4 (FIGS. 4 and 7) greatly increase the buoyancy of the sides and effectively prevent the flooding of the bridge. At the same time, they are not sensitive to puncturing by small arms ammunition, as gas inflated supporting structures would be.

Rolling the sides of the film-foam laminate material into tight rolls (FIG. 4) into cylindrical form provides the increased rigidity to resist the side pressure of the moving water and simultaneously provides increased buoyancy which allows the moving water to flow under the bridge structure.

These side rolls are kept from unrolling by cinch ropes (17) which run under the width of the bridge, over the rolls, and are secured by a hook-type fastener to ring (10).

Incorporation of light weight stilfeners 3 (FIGS. 1, 3 and 5) sealed into the reinforced film-foam laminate 2 during manufacture, provides additional buoyancy as well as increased rigidity in the flow of the floatable bridge construction. These stiffeners may be made of plastic, wood, metal, or any other suitable strong light-weight material. Preferably they are hollow, or cast of cellular metal.

The size of these stiifeners as well as their spacing can be varied to provide the flow rigidity and degree of buoyancy required for its anticipated usage. A personnel bridge would require smaller stilfeners and wide spacing whereas a floatable bridge for jeeps, trucks, artillery, light tanks and the like would require larger as well as more frequent sealed-in stitfeners.

FIG. 7 shows the completed transportation system, including two bridgeheads 11, anchoring bolts 12 attached at the bridgeheads, and the supporting watery medium, 13, and personnel 14, and vehicle 15 in transit.

The cellular plastic foam may be a urethane, or a foamed vinyl halide, or plastisol, or an olefin-sulfone resin, or a polyolefin, such as for example, polyethylene or poly-p ropylene or their coor ter-polymers, or any other polymer of similar properties now known or discovered hereafter. Similarly, these or other polymers such as polyacrylates or methacrylates, polyamids, polyethylene glycol terephthadates, acetal resins and the like may be used as materials or the reinforcing fibers and/or the films.

It is preferred to have the reinforced fibers in the films arranged so as to permit their displacement within the laminate under stress, so that the fibers under stress can bunch together to high strength rope-like bundles, thereby preventing any incipient tear from growing.

Preferably, the rollable buoyant aprons at the sides of the bridge are made of a reinforced laminate of films such as polyvinyl chloride, polyolefin such as polyethylene or polypropylene; polyurethane or the like having reinforcing fibers therebetween, and also having a buoyant core of cellular flexible polymeric foam therebetween for example of any of the above mentioned polymers or the like.

FIG. 6 shows a cross-section of the bridge core material in its general form, 6 being a film, 7 an adhesive softer than the film and 5 the foamed core.

In the construction of the buoyant rollable side aprons, I prefer to employ the construction of FIG. 8, with two film laminates, 16, in which twofilms 20 and 21 com,- bine and adhesive 7 and layers of reinforcing fibers 18 and 19 therein or therewith foamed core 5 therebetween although I may also use the cheaper construction of FIG. 9 with two simple films, a foamed core and reinforcing fibers 18 and 19 preferably in parallel layers, and non-interwoven, between said films on either side of, or within the said polymeric foam 5. The embodiment shown in FIG. 9 has only two surface fihns, and between these reinforcing fibers 18, which may be positioned within a foam 5, as shown, or on either side of it, with or without adhesive. If the foam is formed in place, as is often done particularly with polyurethanes, it is particularly easy to position the fibers in it and to dispense with other adhesives.

It is thus seen that the invention permits considerable variation, both in the choice and disposition of the component materials, and in the proportions and dimensions which can be determined by the skilled user in view of the needs in each case.

Having thus disclosed my invention, I claim:

1. A floating bridge comprising spaced reinforced films with cellular plastic foam therebetween, a plurality of spaced transverse stiifening ribs, the longitudinal edges of said bridge being rolled upwardly and inwardly to form side apron means retaining said rolls in position to form stiffening and protective sides, and a rope through each of said rolls and extending beyond said bridge for 15 anchoring to suitable anchor points on the shore line.

2. The floating bridge of claim 1, the said two reinforced films having reinforcement fibers adapted to bunch together under stress, so as to prevent any tear from propagating.

3. The floating bridge of claim 1, the said reinforced films being made of polyolefin.

4. The floating bridge of claim 1, the said reinforced films being made of a polyvinyl halide.

5. The floating bridge of claim 1, in which the said rolled longitudinal edges have a foamed core comprising a polyurethane.

6. The floating bridge of claim 1, in which the said rolled longitudinal edges have a foamed core comprising a polyolefin.

References Cited UNITED STATES PATENTS 2,527,995 10/ 1950 Hamilton 14-27 2,660,194 11/1953, Hoffman.

2,924, 191- 2/1960 Blumquist 1140.5 3,090,339 5/1963 Carr.

3,147,727 9/1964 Weiss 1140.5 3,340,553 9/1967 Jones 1140.5

JACOB L. NACKENOFF, Primary Examiner US. Cl. X.R. 114-05 

